Ernest p



(No Model.)

' E. P. WARNER.

TELEPHONE EXCHANGE GENTRAL OFFICE CONNECTION. No. 378,030. PatentedPeb. 14, 1888.-

%A IF LU N. PETER8. Pholo-btbowiwn WahlnM DJ;

. UNITED STATES PATENT OFFICE.

v ERNESTP. WARNER, OF, CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERN ELECTRIC COMPANY, OF SAME I LAOE.

TELEPHONE-EXCHANGE CENTRAL-OFFICE CONN ECTIQNL SPBCIPICATION forming part of Letters Patent No. 378,030, dated February 14, 1888.

Application filed November 17, 1887. Serial No. 255,450. (No model.)'

My invention relates to test-battery centraloflice circuits of a multiple switch-board system of a telephone-exchange; and its object is to enable the switchmen to answer calls more rapidly than heretofore, and at the same time avoid including the test-battery in circuit, except at the moment of testing.

Heretoforc on plugging 1nto the switch of a calling subscriber it has been usually necessary to operate a cam-lever switch to bring the telephone and test-battery of the switchman into circuit, the circuit of said battery and telephone being common to all the connectingcords of the particular switchmans section.

My invention consists in placing the switchmans telephone in a ground branch permanently connected with the back contact-strips of the cam-lever switches, the test-battery, as

heretofore, remaining in circuit between the back and the front strips of the cam-lever switches. By this arrangement the groundplates heretofore connected with metallicheels provided on the plugs are dispensed with.

My invention is illustrated in the accompanying drawing, in which I have shown a camlever switch, a pair of cords, the telephone in h a ground branch connected to the back strip,

and a test-battery between the back and front strips of the cam-lever switch. I have not shown the telephone-lines nor the spring-jack switches of the switch-board.

By means of the apparatus shown any desired tests or connections may be made.

The canrlever a being down, the springs b and 0 rest upon back strip, d, and front strip,

6, respectively. The springs are each connected with a different cord of the pair, and the circuit of the test-batteryf is open. The operators telephone 9 is included in a circuit connected from back strip, d, to ground.

It will be seen that the circuit of plug it may be traced to the calling-key i, and thence by wire is to spring I). From plug l the circuitmay be traced to'call ing-key m, and thence by wire 11. to spring 0. p

The switchman on seeing a shutter fall plugs at once into the spring-jack of the calling-line with plug h, and, listening at his telephone, receives the order. Thereupon he tests the line of the subscriber wanted withplug Z.- If the line wanted should be busy, the circuit will be closed through the battery f and telephone g. If he finds that the line is free, he completes the connection and throws up the camlever, disconnecting the test-battery.

Having thus describedpiyinvention, I claim as new and desire to secure by Letters Patent 1. The combination, with a pair of cords and plugs, of a loop-switch and a test-battery in circuit between two contact-points of the switch, and contact-springs normallyresting on said contact-points to close the battery to the cords, and a telephone in a circuit branched from one of the contact-points to ground, substantially as described.

2. The combination, with a pair of cords and plugs, of atelephone included in a branch circuit to ground, a loop-switch, with a battery in circuit between two contacts of the switch, and circuit-changing devices -for'disconnecting the telephone and battery from the cords and connecting the two cords together,

ERNEST P. WARNER.

Witnesses:

GEORGE P. BARTON, WM. M. GILLER. 

